A new RO system needs a short start-up routine before you use the water for drinking. Following it protects the membrane and gives you a clean start.
Why flush first?
New carbon cartridges can release fine carbon dust, and new membranes are shipped with a preservative. A flush removes both. Always follow your system manual if it gives different steps.
Basic start-up steps
- Check that all fittings are tight and the drain line is secure.
- Open the water supply slowly and check for leaks.
- Open the RO faucet and let the system run until water flows.
- Close the faucet and allow the storage tank to fill; this can take a few hours.
- Empty the first tank completely and let it fill again. Many manuals suggest repeating this once or twice.
What to check in the first weeks
- Look for slow leaks at connections.
- Listen for continuous running water, which may mean a valve problem.
- Check the TDS reading of treated water against tap water; see how to test water at home.
- Note the date and plan cartridge changes; see how often to replace cartridges.
Read how reverse osmosis works to understand each stage. Browse residential RO systems and under-sink RO filters, or book professional installation.
First-start checklist for a new RO system
The first hours of a new RO system set the tone for its whole life. Before starting, confirm that the feed water is connected correctly, the drain line is free and the pre-filters are fitted in the right order. Open the feed valve slowly to avoid pressure shocks, and check every joint for drips before you let the system run unattended.
New carbon and membrane elements need flushing. Carbon can release fine dust and membranes are shipped with a preservative, so the first batch of water should go to drain, not to the tank or to drinking. Follow the manufacturer’s flushing time for your model. Then check the output TDS, the flow at the tap and the pressure gauge, and write the values down as a baseline for future comparison.
Start-up checklist
- Check connections and the drain line before opening the feed.
- Fit pre-filters in the correct order and tighten housings by hand, then check for leaks.
- Flush new carbon and membrane to drain for the recommended time.
- Check storage tank pressure, if the system has one.
- Record feed pressure, output TDS and flow as your baseline.
- Note the installation date and set the first filter change reminder. See the RO maintenance schedule.
RO start-up questions
Is the first tank of water safe to drink?
Usually the first tank should be discarded. Flush and sanitise as directed by the manufacturer before drinking.
Why does the water taste flat?
RO water has few minerals and can taste flat to some people. Some systems include a mineral stage if you prefer a different taste.
What if there is a leak or low flow?
Switch off, close the feed and recheck the fittings. Low flow can be caused by pressure, blocked filters or a valve left closed. See low pressure after installing a filter.
We install RO systems and train you on the first start. Visit installation services.
Related reading and products
Related guides
- RO Reject Water: Can You Reuse It at Home?
- Industrial RO Plant Sizing Basics: Capacity, Recovery and Pre-Treatment
- When to Replace an RO Membrane: Signs and Typical Lifespan
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